Timepiece escapement

ABSTRACT

A lever escapement for timepieces includes a guard pin at one end of a pivotable lever, which guard pin at least in part is constituted by a magnet having a predetermined polarity at its free end. The safety roller cooperating with said guard pin is also constituted in part by a magnet the external part of the magnet facing the free end of the guard pin having the same polarity as the latter. The repulsion between the guard pin and the safety roller ensures the maintenance of the lever against a banking pin arranged to one side of the lever.

Inventor Aerschmann Nicholas Geneva, Switzerland Appl. No. 81,402 Filed Oct. 16, 1970 Patented Dec. 28, 1971 Assignee Les F abriques dAssortirnents Renunies S.A. Le Locle, Switzerland Priority Oct. 22, 1969 Switzerland 15745/69 TIMEPIECE ESCAPEMENT 1 Claim, 3 Drawing Figs.

US. Cl 58/122, 58/28 D, 58/116 M, 74/15 Int. Cl ..G04b 15/08, G04b 15/00 Field of Search 58/116 R,

116M,28 D, 28 R, 121 122, 27

[56] References Cited UNITED STATES PATENTS 1,517,008 11/1924 Jones 58/116 R 2,669,089 2/1954 Straumann 58/121 3,059,413 10/1962 Detwiler 58/28 D 3,183,426 5/1965 Haydon.... 58/28 R X 3,446,007 5/1969 Cohen 58/116 X 3,481,138 12/1969 Futagawa et a1 58/28 R Primary Examiner- Richard B. Wilkinson Assistant ExaminerStanley A. Wal Atlorneys Robert E, Burns and Emmanuel .l. Lobato ABSTRACT: A lever escapement for timepieces includes a guard pin at one end of a pivotable lever, which guard pin at least in part is constituted by a magnet having a predetermined polarity at its free end. The safety roller cooperating with said guard pin is also constituted in part by a magnet the external part of the magnet facing the free end of the guard pin having the same polarity as the latter. The repulsion between the guard pin and the safety roller ensures the maintenance of the lever against a banking pin arranged to one side of the lever.

TIMEPIECE ESCAPEMEN'I BACKGROUND OF THE INVENTION The present invention relates to lever escapements for timepieces.

Leer escapements are known which include an escape wheel, a lever or anchor having pallet arms at one end which carry pallets for cooperating with the escape wheel and a fork and a guard pin or dart at the opposite end. The fork cooperates with a table roller provided with an impulse pin and the guard pin cooperates with a safety roller. Such a known lever escapement can be designed to eliminate recoil of the escape wheel but some maintain the feature of recoil, since recoil is necessary when a draw action is required. Draw is an important action in the operational sequence of the lever escapement, whereby, after the instant of locking, the escape wheel tooth continues to advance drawing the pallet firmly so that the lever engages one of a pair of banking pins arranged one on either side of the lever. The tooth holds the lever against release by an external shock or other cause until unlocked. The energy lost during unlocking and the disturbances of the period of the balance caused by the unlocking are relatively important.

The known lever escapements which work without recoil of the escape wheel, are those employing a stable device for maintaining the fork on the two banking pins, the device being a mechanical or magnetic jumper. Alternatively, the two banking pins can be made as magnets The drawback of all the known devices is that the return force on the banking pins decreases according to the distance therefrom of the lever and in the case, where the banking pins are magnets, to the square of the distance, from the lever to the banking pin.

AIMS OF THE INVENTION.

and 9. The lever 6 cooperates by means of fork 7 with an impulse pin 10 supported by a roller table 11 connected to a balance staff not shown. To minimize the effects of shock the fork 7 is provided with a guard pin 12 engageable by a safety roller 13 having a recess 14.

he dead beat surfaces 50 of pallets 5 are formed tangential to the circle passing through the dead beat surface of tooth 2 which has the center on the axis of rotation of the lever 6. Thus, during the unlocking movement of a pallet, the escape wheel I does not recoil, since, because of the small unlocking angle, the tangent and the arc of the circle substantially merge with each other.

For that reason the lever 6 does not receive any draw ensuring maintenance of the fork 7 against the banking pins 8, 9. The maintenance is ensured in the present embodiment by magnetic means. The guard pin 12 is made of magnetic material and magnetized in the longitudinal sense with the end, facing the safety roller 13 having, for example, a negative polarity. The safety roller 13 is also made of a magnetic material and is magnetized in a radial sense in such a way that its whole external surface facing the guard pin has a polarity of An object of the present invention is the production of a lever escapement workingwithout recoil in which the return force of the lever on the banking pins increases according to the distance of said lever from said banking pins.

According to the present invention, a lever escapement for a timepiece comprises an escape wheel, a pivotally mounted lever having at one end pallet arms carrying pallets for cooperation with the escape wheel a fork and a guard pin mounted at the opposite end of the lever, a table roller carrying an impulse pin for engaging the fork and a safety roller having a recess, for engaging the guard pin, the guard pin at least in part being constituted by a magnet having a predetermined polarity at its free end, and the safety roller constituted at least in part by a magnet, the external part of the magnet facing the free end of the guard pin having the same polarity as the latter.

DESCRIPTION OF THE FIGURES OF THE DRAWINGS An embodiment of the invention will now be described, by way of example, reference being made to the figures of the accompanying drawing in which:

FIG. I is a partial plan view of an escapement according to the invention;

FIG. 2 is a partial elevation of the escapement of FIG. 1; and

FIG. 3 is a cross section on the line lll-lll of FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT As shown, a lever escapement comprises a known escape wheel 1 having teeth 2. The impulse face 3 of each tooth 2 successively coacts with an impulse face 4 of a pallet 5 of a pivotable lever 6. At its opposite end, the lever 6 has a fork 7. Movement of the lever 6 is limited by opposed banking pins 8 the same sign as that of the extremity of the guard pin, that is, a negative polarity, in order that a repulsion exists between the safety roller [3 and the guard pin 12. The repulsion ensures the maintenance of the lever 6 against the banking pins 8, 9. The repulsion increases when the guard pin 12 approaches the roller, which can happen in the case of certain shocks. Conversely, the repulsion increases as the distance between the guard pin 12 and the banking pins 8, 9 increases.

In an escapement with a simple safety roller, (now shown) that roller itself would be gradually magnetized and the element acting as a guard pin would serve as a small magnet repelled by the roller.

In a pin lever escapement, it is necessary to change the shape of the tooth insuch a way that the dead beat surface is tangential tothe rotational circle of the lever in order that the draw can be suppressed.

It is to be noticed that during the passage of the guard pin 12 through the recess I4 of the safety roller 13, the repulsion practically ceases because of the recess which does not have a defined magnetic polarity.

The building of such an escapement according to the abovedescribed embodiment presents no difficulty, the small magnets forming the guard pin 12 and safety roller 13 being easily worked in magnetic material, such as, platine-cobalt or Cunife. The safety roller 13 could be formed, then forced on or gripped on a cylindrical part of table roller 11.

Such an escapement is particularly useful in high frequency movements where the number of oscillations in an hour is greater than 30, 000. The saving of energy, permits the assembly of a larger balance with a greater moment of inertia, or a barrel of the same dimension with a more important power reserve.

What is claimed is:

1. In a lever escapement for a timepiece comprising an escape wheel, a pivotally mounted lever having at one end pallet arms carrying pallets for cooperation with the escape wheel, a fork and a guard pin mounted at the opposite end of lever, a table roller carrying an impulse pin for engaging the fork and a safety roller having a recess, for engaging the guard pin, the improvement which comprises the guard pin at least in part, being constituted by a magnet having a predetermined polarity at the free end of the guard pin and the safety roller constituted at least in part, by a magnet, the external part of the magnet facing the free end of the guard pin having the same polarity as the latter.

' UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,630,018 Dated December '28, 1971 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Line 1 of" the Heading, delete "Aer'schmann" and insert -Aeschmann--.

Signed and sealed this 23rd day of January 1973 (SEAL) Attest:

EDWARD M.,PLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-1050 (10-69) v USCOMM-DC 60376-P69 e uis. GOVERNMENT PRINTING omcs: 195s oaes-s34 UNITED STATES PATENT OFFTCE CERTIFICATE OF CORRECTION Patent No. 3,630,018 Dated December 28, 1971 a It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Line 1 of the Heading, delete "Aer'schmann" and insert Aeschmanr1--.

Signed and sealed this 23rd day of January 1973.

(SEAL) Attest:

EDWARD M.,FLETCHER,JR. ROBERT GOTTSCHA-LK Attesting Officer Commissioner of Patents FORM PO-1050 (10-69) USCOMM DC 60376-P69 u.s. GOVERNMENT PRINTING OFFICE: I969 0-386-334 

1. In a lever escapement for a timepiece comprising an escape wheel, a pivotally mounted lever having at one end pallet arms carrying pallets for cooperation with the escape wheel, a fork and a guard pin mounted at the opposite end of lever, a table roller carrying an impulse pin for engaging the fork and a safety Roller having a recess, for engaging the guard pin, the improvement which comprises the guard pin at least in part, being constituted by a magnet having a predetermined polarity at the free end of the guard pin and the safety roller constituted at least in part, by a magnet, the external part of the magnet facing the free end of the guard pin having the same polarity as the latter. 